Not sure if this is common knowledge or not... but when comparing different Thick PBT keycaps I noticed something really neat about the Vortex set I purchased recently. It appears that in their molds they have included an indentation on the inner lip of the cap to avoid rubbing with costar stabilizers.

These Vortex caps are actually 1.5mm, the same thickness as a similar set that I purchased from Leopold. However, the Leopold keycaps do not have an indentation and rub on the costar wire while these Vortex ones do not!
Just thought I'd share my observations with the rest of you. I now have a whole new appreciation for Vortex.